An electrophotographic image-forming device capable of performing a multicolor printing includes a plurality of photoconductors and a plurality of chargers opposed to the plurality of photoconductors, respectively. When voltages are applied to the plurality of chargers, corona discharges occur at the plurality of chargers to charge the plurality of photoconductors. When a wire of the charger becomes contaminated with airborne (accumulated) dust particles or other contaminants around the charger, an abnormal discharge. Therefore, an image-forming device that, when detecting the occurrence of the abnormal discharge, acquires the voltages applied to the plurality of chargers, sequentially changes the voltages applied to the plurality of chargers, and identifies, based on the voltage changing result, the charger at which the abnormal discharge is occurring, is proposed.